Substrate cleaning apparatus and substrate cleaning method

ABSTRACT

A substrate cleaning apparatus performs scrub cleaning of a surface of a substrate with an elongated cylindrical roll cleaning member. The substrate cleaning apparatus includes a roll holder for supporting the cleaning member and rotate the roll cleaning member, a vertical movement mechanism for vertically moving the roll holder so that the roll cleaning member applies a roll load to the substrate at the time of cleaning the substrate by actuation of an actuator having a regulating device, a load cell for measuring the roll load, and a controller for performing feedback control of the roll load through the regulating device based on the measured value of the load cell. The substrate cleaning apparatus further includes a monitor unit for monitoring whether an operation amount of the regulating device falls outside an allowable range of a preset reference value of an operation amount corresponding to a preset roll load.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.14/061,686 filed Oct. 23, 2013; the entire contents are incorporatedherein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a substrate cleaning apparatus and asubstrate cleaning method for performing scrub cleaning of a surface ofa substrate, such as a semiconductor wafer, with an elongatedcylindrical roll cleaning member extending horizontally, by rotating thesubstrate and the roll cleaning member each in one direction whilekeeping the roll cleaning member in contact with the surface of thesubstrate.

Description of the Related Art

In a cleaning apparatus for performing scrub cleaning of a surface of asubstrate, such as a semiconductor wafer, with a roll cleaning member,the roll cleaning member is rotated and pressed against the substrateunder a predetermined pressing load (roll load) during cleaning of thesubstrate. Controlling and adjusting the roll load to an appropriatevalue is important to increase the cleanliness of the substrate or toprevent the substrate from being damaged.

Therefore, the applicant of the present invention has proposed asubstrate cleaning apparatus having a closed-loop feedback control (CLC)system in which the pressing load (roll load) for pressing the rollcleaning member against the substrate is measured by a load cell duringcleaning of the substrate to control a regulating device of an actuator,such as a motor, based on the measured values, thereby controlling theroll load to an appropriate value by feedback control, as disclosed inJapanese laid-open patent publication No. 2002-50602.

In the case where the pressing load (roll load) for pressing the rollcleaning member against the substrate is measured by the load cell tocontrol the roll load based on the measured values by feedback controlduring cleaning of the substrate, if the roll load is not measuredaccurately due to breakdown of the load cell, an appropriate roll loadcannot be applied to the substrate by the roll cleaning member.

Specifically, if the measured value (measured roll load) of the loadcell becomes larger than the actual roll load due to breakdown of theload cell, a roll load which is smaller than the predetermined roll loadis applied to the substrate by the roll cleaning member, thus reducingthe cleaning ability for the substrate. On the other hand, if themeasured value (measured roll load) of the load cell becomes smallerthan the actual roll load, a roll load which is larger than thepredetermined roll load is applied to the substrate by the roll cleaningmember, thus possibly causing breakage of the substrate.

SUMMARY OF THE INVENTION

Based on the above knowledge obtained from various experiments, thepresent invention has been made. It is therefore an object of thepresent invention to provide a substrate cleaning apparatus and asubstrate cleaning method which can rapidly detect breakdown of a loadcell for measuring a roll load during cleaning of a substrate, toprevent the cleaning of the substrate, in a state in which an abnormalroll load is applied to the substrate by a roll cleaning member, frombeing continued.

In order to achieve the above object, according to an aspect of thepresent invention, there is provided a substrate cleaning apparatus forcleaning a substrate, comprising: a roll holder configured to support ahorizontally elongated roll cleaning member and rotate the roll cleaningmember; a vertical movement mechanism configured to vertically move theroll holder so that the roll cleaning member applies a roll load to thesubstrate at the time of cleaning the substrate by actuation of anactuator having a regulating device; a load cell configured to measurethe roll load; a controller configured to perform feedback control ofthe roll load through the regulating device based on the measured valueof the load cell; and a monitor unit configured to monitor whether anoperation amount of the regulating device falls outside an allowablerange of a preset reference value of an operation amount correspondingto a preset roll load.

If the load cell for measuring the roll load breaks down to cause anerror in the measured value of the load cell, the operation amount ofthe regulating device is deviated from the preset reference value of theoperation amount corresponding to the preset roll load. Therefore, themonitor unit monitors whether the operation amount of the regulatingdevice falls outside the allowable range of the preset reference valueof the operation amount corresponding to the preset roll load, therebydetecting breakdown of the load cell promptly during cleaning of thesubstrate.

In a preferred aspect of the present invention, the substrate cleaningapparatus further comprises an alarm configured to issue an alarm whenthe operation amount of the regulating device falls outside theallowable range of the preset reference value of the operation amountcorresponding to the preset roll load.

In a preferred aspect of the present invention, the actuator comprisesan air cylinder, and the regulating device comprises an electropneumaticregulator configured to control a valve opening degree of a regulatingvalve for regulating a pressure of air to be supplied to the aircylinder.

According to another aspect of the present invention, there is provideda substrate cleaning method for cleaning a substrate, comprising:applying a roll load to the substrate by a horizontally elongated rollcleaning member configured to be moved vertically by actuation of anactuator having a regulating device; measuring the roll load applied tothe substrate by a load cell; and monitoring whether an operation amountof the regulating device falls outside an allowable range of a presetreference value of an operation amount corresponding to a preset rollload while performing feedback control of the roll load through theregulating device based on the measured value of the load cell.

In a preferred aspect of the present invention, the substrate cleaningmethod further comprises issuing an alarm when the operation amount ofthe regulating device falls outside the allowable range of the presetreference value of the operation amount corresponding to the preset rollload.

According to the present invention, the monitor unit monitors whetherthe operation amount of the regulating device falls outside theallowable range of the preset reference value of the operation amountcorresponding to the preset roll load, thereby detecting breakdown ofthe load cell promptly during cleaning of the substrate. In this manner,the cleaning of the substrate in a state in which an abnormal roll loadis applied to the substrate by the roll cleaning member can be preventedfrom being continued.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing an entire structure of a substrateprocessing apparatus incorporating a substrate cleaning apparatusaccording to an embodiment of the present invention;

FIG. 2 is a schematic perspective view showing the substrate cleaningapparatus, according to an embodiment of the present invention, which isincorporated in the substrate processing apparatus shown in FIG. 1;

FIG. 3 is a schematic elevational view showing an entire structure ofthe substrate cleaning apparatus according to the embodiment of thepresent invention;

FIG. 4 is a graph showing an example of the relationship between apreset roll load (N), a reference value of a valve-operation-amount(kPa) of an electropneumatic regulator, and an allowable range of thereference value;

FIG. 5 is a graph showing another example of the relationship betweenthe preset roll load (N), the reference value of thevalve-operation-amount (kPa) of the electropneumatic regulator, and theallowable range of the reference value; and

FIG. 6 is a flow chart showing an embodiment of control for cleaning thefront surface (upper surface) of the substrate while performing feedbackcontrol of a roll load applied to the substrate by an upper rollcleaning member of the substrate cleaning apparatus shown in FIG. 3.

DETAILED DESCRIPTION

A substrate cleaning apparatus and a substrate cleaning method accordingto embodiments of the present invention will be described below withreference to FIGS. 1 through 6.

FIG. 1 is a plan view showing an entire structure of a substrateprocessing apparatus incorporating a substrate cleaning apparatusaccording to an embodiment of the present invention. As shown in FIG. 1,the substrate processing apparatus includes a generally-rectangularhousing 10, and a loading port 12 for placing thereon a substratecassette storing a large number of substrates, such as semiconductorwafers. The loading port 12 is disposed adjacent to the housing 10 andis capable of placing thereon an open cassette, a SMIF (standardmanufacturing interface) pod or a FOUP (front opening unified pod). Eachof the SMIF and the FOUP is a hermetically sealed container which housestherein a substrate cassette and is covered with a partition wall, andthus can keep independent internal environment isolated from an externalspace.

In the housing 10, there are provided a plurality of (four in thisembodiment) polishing units 14 a, 14 b, 14 c, 14 d, a first substratecleaning unit 16 and a second substrate cleaning unit 18 each forcleaning a substrate after polishing, and a substrate drying unit 20 fordrying a substrate after cleaning. The polishing units 14 a, 14 b, 14 c,14 d are arranged in the longitudinal direction of the substrateprocessing apparatus, and the substrate cleaning units 16, 18 and thesubstrate drying unit 20 are also arranged in the longitudinal directionof the substrate processing apparatus. The substrate cleaning apparatusaccording to the embodiment of the present invention is applied to thefirst substrate cleaning unit 16.

A first substrate transfer robot 22 is disposed in an area surrounded bythe loading port 12, and the polishing unit 14 a and the substratedrying unit 20 which are located near the loading port 12. Further, asubstrate transport unit 24 is disposed in parallel to the polishingunits 14 a, 14 b, 14 c, 14 d. The first substrate transfer robot 22receives a substrate before polishing from the loading port 12 andtransfers the substrate to the substrate transport unit 24, and receivesa substrate after drying from the substrate drying unit 20 and returnsthe substrate to the loading port 12. The substrate transport unit 24transports a substrate transferred from the first substrate transferrobot 22, and transfers the substrate between the substrate transportunit 24 and the polishing units 14 a, 14 b, 14 c, 14 d.

Between the first substrate cleaning unit 16 and the second substratecleaning unit 18, there is provided a second substrate transfer robot 26for transferring a substrate between the first substrate cleaning unit16 and the second substrate cleaning unit 18. Between the secondsubstrate cleaning unit 18 and the substrate drying unit 20, there isprovided a third substrate transfer robot 28 for transferring asubstrate between the second substrate cleaning unit 18 and thesubstrate drying unit 20. In the housing 10, there is provided a controlpanel (operation panel) 30 for setting a controller 66, inputting apreset value of the roll load (instructing a preset roll load), and thelike, described below.

FIG. 2 is a schematic perspective view showing the substrate cleaningapparatus (first substrate cleaning unit 16), according to an embodimentof the present invention, incorporated in the substrate processingapparatus shown in FIG. 1. FIG. 3 is a schematic elevational viewshowing an entire structure of the substrate cleaning apparatus 16according to the embodiment of the present invention.

As shown in FIGS. 2 and 3, the substrate cleaning unit 16 includes aplurality of (four as illustrated) horizontally movable spindles 40 forsupporting a periphery of a substrate W, such as a semiconductor wafer,with its front surface facing upwardly, and horizontally rotating thesubstrate W, a vertically movable upper roll holder 42 disposed abovethe substrate W rotatably supported by the spindles 40, and a verticallymovable lower roll holder 44 disposed below the substrate W rotatablysupported by the spindles 40.

An elongated cylindrical upper roll cleaning member (roll sponge) 46made of PVA or the like, is rotatably supported by the upper roll holder42. The upper roll cleaning member 46 is rotated by a driving mechanism(not shown) in the direction shown by the arrow F₁ in FIG. 2. Anelongated cylindrical lower roll cleaning member (roll sponge) 48, madeof PVA or the like, is rotatably supported by the lower roll holder 44.The lower roll cleaning member 48 is rotated by a driving mechanism (notshown) in the direction shown by the arrow F₂ in FIG. 2.

An upper cleaning liquid supply nozzle 50 for supplying a cleaningliquid onto the front surface (upper surface) of the substrate W isdisposed above the substrate W rotatably supported by the spindles 40. Alower cleaning liquid supply nozzle 52 for supplying a cleaning liquidonto the back surface (lower surface) of the substrate W is disposedbelow the substrate W rotatably supported by the spindles 40.

A concave portion 42 a is provided at a substantially central area alongthe longitudinal direction of the upper roll holder 42, and a load cell54 is located inside of the concave portion 42 a and is fixed to theupper roll holder 42. In this example, there is provided a verticalmovement mechanism 60 comprising an air cylinder 56 disposed in thevertical direction to serve as an actuator, a vertically movable shaft57 vertically movable by actuation of the air cylinder (actuator) 56,and a vertically movable arm 58, as a vertically movable unit, extendingin the horizontal direction and having a base end connected to the upperend of the vertically movable shaft 57. The upper roll holder 42 iscoupled via the load cell 54 to a lower end of a free end side of thevertically movable arm (vertically movable unit) 58. A tilting mechanism70 for tilting the upper roll holder 42 is disposed between the loadcell 54 and the lower surface of the free end side of the verticallymovable arm 58.

With this configuration, the upper roll holder 42 is vertically movedtogether with the vertically movable shaft 57 and the vertically movablearm 58, by actuation of the air cylinder 56. The air cylinder 56 isprovided with an electropneumatic regulator 62, as a regulating device,for regulating a pressure of air to be supplied to an interior of theair cylinder 56. By adjusting a valve opening degree of theelectropneumatic regulator (regulating device) 62, the pressure of airto be supplied into the air cylinder 56 is regulated.

In this manner, the upper roll holder 42 is coupled to the lower surfaceof the free end side of the vertically movable arm 58 at thesubstantially central area along the longitudinal direction of the upperroll holder 42 so that a vertical line, passing through the center ofgravity of the upper roll holder 42 which supports and rotates the upperroll cleaning member 46, passes through the center of the load cell 54or a location close to the center of the load cell 54, thereby couplingthe upper roll holder 42 to the lower surface of the free end side ofthe vertically movable arm 58 in a horizontal state and a well-balancedmanner.

Further, the own weight of the upper roll holder 42 can be transmittedto the load cell 54 without any loss by coupling the upper roll holder42 to the lower surface of the free end side of the vertically movablearm 58 via the load cell 54. When the upper roll holder 42 is lowered tobring the upper roll cleaning member 46 into contact with the substrateW at the time of cleaning the substrate W, a tensile load applied to theload cell 54 is reduced by a certain amount which substantiallycoincides with the roll load (pressing load) applied to the substrate Wby the upper roll cleaning member 46.

Accordingly, the roll load applied to the substrate W by the upper rollcleaning member 46 during cleaning of the substrate W is measured by theload cell 54 based on the reduced tensile load and the valve openingdegree is adjusted by an operation amount of the electropneumaticregulator 62, thereby regulating the roll load.

The measured value measured by the load cell 54 is outputted to anindicator 64, and an analog signal is sent from the indicator 64 to thecontroller 66 as a control unit. Then, the analog signal sent from thecontroller (control unit) 66 is inputted to the electropneumaticregulator 62. Thus, a closed-loop control system for performing aclosed-loop control is constructed. Further, a preset value of the rollload (preset roll load) and the like are inputted from the control panel(operation panel) 30 to the controller 66.

With this configuration, the controller 66 compares the measured value(measured roll load) measured by the load cell 54 and the preset rollload inputted from the control panel (operation panel) 30 and gives theelectropneumatic regulator 62 an instruction of an operation amount of aregulating valve (valve-operation-amount) for the air cylinder,depending on a difference between the measured roll load and the presetroll load. The electropneumatic regulator 62 automatically adjusts thevalve opening degree of the regulating valve in response to theinstruction from the controller 66 to vary a thrust force of the aircylinder 56 with the adjusted valve opening degree, thereby performingfeedback control of the roll load applied to the substrate W duringcleaning of the substrate W.

According to this example, the load cell 54 is provided between thevertically movable arm 58 of the vertical movement mechanism 60 and theupper roll holder 42 coupled to the vertically movable arm 58, and theload cell 54 is configured to receive the own weight of the upper rollholder 42. Further, a bearing or a link rod which increases frictionduring vertical movement of the upper roll holder 42, or a beamstructure or projection which causes a loss in load transmission, is notprovided between the upper roll holder 42 and the load cell 54. Thus,the roll load applied to the substrate W during cleaning of thesubstrate is transmitted to the load cell 54 accurately, therebymeasuring the roll load with high accuracy and controlling the rollload.

If the load cell 54 breaks down during cleaning of the substrate W whilemeasuring the roll load by the load cell 54, the accurate roll loadcannot be measured, and thus an appropriate roll load cannot be appliedto the substrate W by the upper roll cleaning member 46. Accordingly,the breakdown of the load cell 54 causes an error in the measured value(measured roll load) of the load cell 54, and thus a currentvalve-operation-amount of the electropneumatic regulator 62, i.e. avalve-operation-amount outputted from the controller 66 to theelectropneumatic regulator 62, is deviated from a preset reference valueof the valve-operation-amount depending on the preset roll load.

Thus, in this example, a monitor unit 80 connected to the controller 66monitors whether the valve-operation-amount outputted to theelectropneumatic regulator 62 falls outside an allowable range of thepreset reference value of the valve-operation-amount depending on thepreset roll load, thereby detecting breakdown of the load cell 54promptly during cleaning of the substrate W.

Specifically, the reference value of the valve-operation-amount for eachof the preset roll loads inputted from the control panel 30 to thecontroller 66, is inputted in advance and stored in the monitor unit 80,and the valve-operation-amount outputted from the controller 66 to theelectropneumatic regulator 62 is inputted to the monitor unit 80. Then,the monitor unit 80 monitors whether the valve-operation-amountoutputted to the electropneumatic regulator 62 falls outside theallowable range of the reference value of the valve-operation-amountcorresponding to the preset roll load inputted from the control panel 30to the controller 66. When the monitor unit 80 detects breakdown of theload cell 54, the monitor unit 80 outputs a signal to an alarm 82connected to the monitor unit 80, and then the alarm 82 issues an alarmin response to the signal.

FIG. 4 shows an example of the relationship between the preset roll load(N), the reference value of the valve-operation-amount (kPa) of theelectropneumatic regulator, and the allowable range of the referencevalue. In this example, the reference values of thevalve-operation-amount (kPa), of the electropneumatic regulator,corresponding to the respective preset roll loads (N) are shown by alinearly-extending line A. A linearly extending line B obtained bysubtracting a constant value from the line A shows lower thresholds, anda linearly extending line C obtained by adding a constant value to theline A shows upper thresholds. A range between the line B (lowerthresholds) and the line C (upper thresholds) is determined as anallowable range.

Specifically, in the case where the preset roll load instructed from thecontrol panel 30 to the controller 66 is R (N), the reference value ofthe valve-operation-amount of the electropneumatic regulator 62corresponding to the preset roll load is S (kPa) which is anintersection of the preset roll load R with the line A, and theallowable range of the reference value S of the valve-operation-amountis the range (T1 to T2) between the lower threshold T1 (kPa) which is anintersection of the preset roll load R with the line B and the upperthreshold T2 (kPa) which is an intersection of the preset roll load Rwith the line C.

Each of the preset roll loads (N) and each of the reference values ofthe valve-operation-amount (kPa) of the electropneumatic regulator maybe one-to-one correspondence.

When the substrate W is actually being cleaned while controlling theroll load applied to the substrate W by the upper roll cleaning member46 to the preset roll load R, the monitor unit 80 judges that the loadcell 54 operates normally if the valve-operation-amount (kPa) outputtedfrom the controller 66 to the electropneumatic regulator 62 falls withinthe allowable range (T1 to T2), and judges that the load cell 54 breaksdown if the valve-operation-amount falls outside the allowable range (T1to T2), i.e. the valve-operation-amount becomes smaller than the lowerthreshold T1 or larger than the upper threshold T2.

FIG. 5 shows another example of the relationship between the preset rollload (N), the reference value of the valve-operation-amount (kPa) of theelectropneumatic regulator, and the allowable range of the referencevalue. In this example, the reference values of thevalve-operation-amount (kPa), of the electropneumatic regulator,corresponding to the respective preset roll loads (N) are shown by alinearly-extending line A. A linearly extending line D obtained bysubtracting a constant percentage (%) from the line A shows lowerthresholds, and a linearly extending line E obtained by adding aconstant percentage (%) to the line A shows upper thresholds. A rangebetween the line D (lower threshold) and the line E (upper threshold) isdetermined as an allowable range.

Specifically, in the case where the preset roll load instructed from thecontrol panel 30 to the controller 66 is R (N), the reference value ofthe valve-operation-amount of the electropneumatic regulator 62corresponding to the preset roll load is S (kPa) which is anintersection of the preset roll load R with the line A, and theallowable range of the reference value S of the valve-operation-amountis the range (T3 to T4) between the lower threshold T3 (kPa) which is anintersection of the preset roll load R with the line D and the upperthreshold T4 (kPa) which is an intersection of the preset roll load Rwith the line E.

As shown in FIG. 3, a concave portion 44 a is provided at asubstantially central area along the longitudinal direction of the lowerroll holder 44. The lower roll holder 44 has a vertical movementmechanism 60 a comprising an air cylinder 56 a disposed in the verticaldirection to serve as an actuator, and a vertically movable shaft 59 asa vertically movable unit vertically movable by actuation of the aircylinder (actuator) 56 a. The lower roll holder 44 is coupled via a loadcell 54 a to an upper end surface of the vertically movable shaft(vertically movable unit) 59. With this configuration, the lower rollholder 44 is vertically moved together with the vertically movable shaft59 by actuation of the air cylinder 56 a. The air cylinder 56 a isprovided with an electropneumatic regulator 62 a serving as a regulatingdevice, in the same manner as the above. A tilting mechanism 70 a fortilting the lower roll holder 44 is disposed between the load cell 54 afixed to the upper end surface of the vertically movable shaft 59 andthe lower roll holder 44.

In this manner, the lower roll holder 44 is coupled to the upper endsurface of the vertically movable shaft 59 at the substantially centralarea along the longitudinal direction of the lower roll holder 44 sothat a vertical line, passing through the center of gravity of the lowerroll holder 44 which supports and rotates the lower roll cleaning member48, passes through the center of the load cell 54 a or a location closedto the center of the load cell 54 a, thereby coupling the lower rollholder 44 to the vertically movable shaft 59 in a horizontal state and awell-balanced manner.

Further, the own weight of the lower roll holder 44 can be transmittedto the load cell 54 a without any loss by coupling the lower roll holder44 to the upper end surface of the vertically movable shaft 59 via theload cell 54 a. When the lower roll holder 44 is lifted to bring thelower roll cleaning member 48 into contact with the substrate W, acompressive load applied to the load cell 54 a is increased by a certainamount which substantially coincides with the roll load (pressing load)applied to the substrate W by the lower roll cleaning member 48.

Accordingly, the roll load applied to the substrate W by the lower rollcleaning member 48 during cleaning of the substrate W is measured by theload cell 54 a based on the increased compressive load and the valveopening degree is adjusted by an operation amount of theelectropneumatic regulator (regulating device) 62 a, thereby regulatingthe roll load.

The measured value measured by the load cell 54 a is outputted to anindicator 64 a, and an analog signal is sent from the indicator 64 a tothe controller 66. Then, the analog signal sent from the controller 66is inputted to the electropneumatic regulator 62 a. Thus, a closed-loopcontrol system for performing a closed-loop control is constructed.Further, a preset value of the roll load (preset roll load) is inputtedfrom the control panel (operation panel) 30 to the controller 66.

With this configuration, the controller 66 compares the measured value(measured roll load) measured by the load cell 54 a and the preset rollload inputted from the control panel (operation panel) 30 and gives theelectropneumatic regulator 62 a an instruction of an operation amount ofa regulating valve (valve-operation-amount) depending on a differencebetween the measured roll load and the preset roll load. Theelectropneumatic regulator 62 a automatically adjusts the valve openingdegree in response to the instruction from the controller 66 to vary athrust force of the air cylinder 56 a with the adjusted valve openingdegree, thereby performing feedback control of the roll load applied tothe substrate W during cleaning of the substrate W.

According to this example, the load cell 54 a is provided between thevertically movable shaft 59 of the vertical movement mechanism 60 a andthe lower roll holder 44 coupled to the vertically movable shaft 59 andthe load cell 54 a is configured to receive the own weight of the lowerroll holder 44. Further, a bearing or a link rod which increasesfriction during vertical movement of the lower roll holder 44, or a beamstructure or a projection which causes a loss in load transmission, isnot provided between the lower roll holder 44 and the load cell 54 a.Thus, the roll load applied to the substrate W during cleaning of thesubstrate is transmitted to the load cell 54 a accurately, therebymeasuring the roll load with high accuracy and controlling the rollload.

If the load cell 54 a breaks down during cleaning of the substrate Wwhile measuring the roll load by the load cell 54 a, the accurate rollload cannot be measured, and thus an appropriate roll load cannot beapplied to the substrate W by the lower roll cleaning member 44.

Therefore, as described above, the monitor unit 80 connected to thecontroller 66 monitors whether the valve-operation-amount of theelectropneumatic regulator 62 a falls outside an allowable range of thereference value of the valve-operation-amount depending on the presetroll load, thereby detecting breakdown of the load cell 54 a promptlyduring cleaning of the substrate W. When the monitor unit 80 detects thebreakdown of the load cell 54 a, an alarm is issued from the alarm 82.

In the substrate cleaning apparatus (scrub cleaning apparatus) havingthe above structure, as shown in FIG. 2, a peripheral portion of thesubstrate W is located in an engagement groove 90 a formed in acircumferential surface of a spinning top 90 provided at an upperportion of each of the spindles 40. By spinning (rotating) the spinningtops 90 while pressing them inwardly against the peripheral portion ofthe substrate W, the substrate W is rotated horizontally in thedirection shown by the arrow E in FIG. 2. In this embodiment, two of thefour spinning tops 90 apply a rotational force to the substrate W, whilethe other two spinning tops 90 function as a bearing for supporting therotation of the substrate W. It is also possible to couple all thespinning tops 90 to a drive mechanism so that they all apply arotational force to the substrate W.

While horizontally rotating the substrate W and supplying a cleaningliquid (chemical liquid) from the upper cleaning liquid supply nozzle 50to the front surface (upper surface) of the substrate W, the upper rollcleaning member 46 is rotated and lowered to be brought into contactwith the front surface of the rotating substrate W under a predeterminedroll load, thereby performing scrub cleaning of the front surface of thesubstrate W with the upper roll cleaning member 46 in the presence ofthe cleaning liquid. The length of the upper roll cleaning member 46 isset to be slightly larger than the diameter of the substrate W, and thusthe entire length of the front surface of the substrate W in adiametrical direction, from one end to the other end of the substrate Wcan be cleaned at the same time.

When the front surface of the substrate W is scrub-cleaned with theupper roll cleaning member 46, the roll load applied to the substrate Wby the upper roll cleaning member 46 is measured by the load cell 54.The controller 66 compares the measured value (measured roll load) andthe preset roll load which has been inputted from the control panel 30,and gives an instruction of the operation amount of the regulating valve(valve-operation-amount) to the electropneumatic regulator 62 dependingon a difference between the measured roll load and the preset roll load.The electropneumatic regulator 62 automatically adjusts the valveopening degree in response to the instruction from the controller 66 tovary a thrust force of the air cylinder 56 with the adjusted valveopening degree. Accordingly, the roll load applied to the substrate Wduring cleaning of the substrate W is feedback-controlled so that theroll load becomes equal to the preset roll load.

FIG. 6 is a flow chart showing an embodiment of the control for cleaningthe front surface (upper surface) of the substrate W while performingfeedback control of the roll load applied to the substrate W by theupper roll cleaning member 46 of the substrate cleaning apparatus shownin FIG. 3. An embodiment of the control for cleaning the back surface(lower surface) of the substrate W while performing feedback control ofthe roll load applied to the substrate W by the lower roll cleaningmember 48 of the substrate cleaning apparatus shown in FIG. 3 issubstantially the same as the above, and therefore the explanation willbe omitted hereinafter.

As shown in FIG. 6, the reference values of the valve-operation-amountof the electropneumatic regulator 62 corresponding to the respectivepreset roll loads, e.g. values on the line A shown in FIG. 4 or FIG. 5,are inputted from the control panel 30, and these reference values ofthe valve-operation-amount (line A) are stored in the monitor unit 80(step 1). Then, the roll load (preset roll load), which should beapplied to the substrate W from the upper roll cleaning member 46 duringcleaning, e.g. the preset roll load R (N) shown in FIG. 4 or FIG. 5 isinputted from the control panel 30 to the controller 66 (step 2).

Next, while horizontally rotating the substrate W and supplying acleaning liquid (chemical liquid) from the upper cleaning liquid supplynozzle 50 to the front surface (upper surface) of the substrate W, theupper roll cleaning member 46 is rotated and lowered to be brought intocontact with the front surface of the rotating substrate W, therebyperforming scrub cleaning of the front surface of the substrate W withthe upper roll cleaning member 46 in the presence of the cleaningliquid. The roll load applied to the substrate W during cleaning of thesubstrate W is feedback-controlled so that the roll load becomes equalto the preset roll load (step 3).

The monitor unit 80 compares the reference value of thevalve-operation-amount, of the stored reference values of thevalve-operation-amount, corresponding to the preset roll load, e.g. thereference value S of the valve-operation-amount at which the preset rollload R (N) intersects with the line A (the reference value of thevalve-operation-amount) shown in FIG. 4 or FIG. 5, and thevalve-operation-amount (current valve-operation-amount) which isoutputted from the controller 66 to the electropneumatic regulator 62(step 4). Then, the monitor unit 80 judges whether the currentvalve-operation-amount falls outside the allowable range of thereference value of the valve-operation-amount corresponding to thepreset roll load. For example, the monitor unit 80 judges whether thevalve-operation-amount falls outside the range (T1 to T2) shown in FIG.4 between the lower threshold T1 (kPa) as an intersection at which thepreset roll load R intersects with the line B, and the upper thresholdT2 (kPa) as an intersection at which the preset roll load R intersectswith the line C, or the range (T3 to T4) shown in FIG. 5 between thelower threshold T3 (kPa) as an intersection at which the preset rollload R intersects with the line D, and the upper threshold T4 (kPa) asan intersection at which the preset roll load R intersects with the lineE (steps).

When the current valve-operation-amount falls outside the allowablerange of the reference value of the valve-operation-amount correspondingto the preset roll load, e.g. the current valve-operation-amount becomessmaller than the lower threshold T1 (kPa) shown in FIG. 4 or the lowerthreshold T3 (kPa) shown in FIG. 5, or the currentvalve-operation-amount becomes larger than the upper threshold T2 (kPa)shown in FIG. 4 or the upper threshold T4 (kPa) shown in FIG. 5, themonitor unit 80 judges breakdown of the load cell 54 and issues an alarmfrom the alarm 82 (step 6). Then, the cleaning process is forciblyterminated and the apparatus running is stopped after retrieving thesubstrates inside the apparatus (step 7).

On the other hand, when the current valve-operation-amount does not falloutside the allowable range of the reference value of thevalve-operation-amount corresponding to the preset roll load, themonitor unit 80 judges whether a predetermined cleaning time has elapsed(step 8). If the predetermined cleaning time has not elapsed, theprocessing is returned to step 4. If the predetermined cleaning time haselapsed, the cleaning is terminated (step 9). Then, a process of asubsequent substrate is started (step 10), and the processing isreturned to step 2.

In this manner, the breakdown of the load cell 54 can be detectedpromptly during cleaning of the substrate W, and the cleaning of thesubstrate in a state in which an abnormal roll load is applied to thesubstrate W by the roll cleaning member 46 can be prevented from beingcontinued.

Simultaneously, while supplying a cleaning liquid (chemical liquid) fromthe lower cleaning liquid supply nozzle 52 to the back surface (lowersurface) of the substrate W, the lower roll cleaning member 48 isrotated and raised to be brought into contact with the back surface ofthe rotating substrate W under a predetermined roll load, therebyperforming scrub cleaning of the back surface of the substrate W withthe lower roll cleaning member 48 in the presence of the cleaningliquid. The length of the lower roll cleaning member 48 is set to beslightly larger than the diameter of the substrate W, and thus theentire back surface of the substrate W is cleaned, as with theabove-described cleaning of the front surface of the substrate W.

During scrub cleaning of the back surface of the substrate W with thelower roll cleaning member 48, the roll load applied to the substrate Wduring cleaning of the substrate W is feedback-controlled so that theroll load becomes equal to the preset roll load, as with the case of theabove-described upper roll cleaning member 46.

In the substrate processing apparatus shown in FIG. 1, the substratetaken out from a substrate cassette inside the loading port 12 istransferred to one of the polishing units 14 a, 14 b, 14 c, 14 d, andthe surface of the substrate is polished by the specified polishingunit. The surface of the substrate which has been polished is cleaned(primarily cleaned) in the first substrate cleaning unit 16, and is thencleaned (finally cleaned) in the second substrate cleaning unit 18.Then, the cleaned substrate is removed from the second substratecleaning unit 18 and transferred to the substrate drying unit 20 wherethe substrate is spin-dried. Thereafter, the dried substrate is returnedinto the substrate cassette inside the loading port 12.

In the above examples, although both of the roll load applied to thefront surface (upper surface) of the substrate by the upper rollcleaning member 46 and the roll load applied to the back surface (lowersurface) of the substrate by the lower roll cleaning member 48 arefeedback-controlled using a closed-loop control system, either one ofthem may be feedback-controlled depending on use conditions (process,property of the substrate, pressing load, and the like).

Although preferred embodiments have been described in detail above, itshould be understood that the present invention is not limited to theillustrated embodiments, but many changes and modifications can be madetherein without departing from the appended claims.

What is claimed is:
 1. A substrate cleaning apparatus for cleaning asubstrate, comprising: a roll holder configured to support a rollcleaning member and rotate said roll cleaning member; a movementmechanism having an actuator and a regulating device configured toregulate output of the actuator, said movement mechanism beingconfigured to move said roll holder so that said roll cleaning memberapplies a roll load to the substrate at the time of cleaning thesubstrate by actuation of said actuator; a load cell configured tomeasure said roll load; a controller configured to perform feedbackcontrol of said roll load through said regulating device based on themeasured value of said load cell, wherein said feedback control isperformed so that said controller outputs an operation amount to saidregulating device depending on a difference between the measured valueof said load cell and a preset roll load; and a monitor unit configuredto monitor whether said operation amount outputted to said regulatingdevice falls outside a preset allowable range of operation amount andconfigured to detect said operation amount falling outside said presetallowable range, wherein said monitor unit outputs a signal when saidoperation amount outputted to said regulating device falls outside saidpreset allowable range of operation amount.
 2. A substrate cleaningapparatus according to claim 1, wherein said actuator comprises an aircylinder, and said regulating device comprises an electropneumaticregulator configured to control a valve opening degree of a regulatingvalve for regulating a pressure of air to be supplied to said aircylinder.
 3. A substrate cleaning apparatus according to claim 1,wherein said monitor unit outputs said signal to an alarm when saidoperation amount outputted to said regulating device falls outside saidpreset allowable range of operation amount, and said alarm issues analarm in response to said signal.
 4. A substrate cleaning apparatusaccording to claim 1, wherein said roll cleaning member is elongatedhorizontally.
 5. A substrate cleaning apparatus according to claim 1,wherein said movement mechanism is configured to move said roll holdervertically.
 6. A substrate cleaning apparatus according to claim 1,wherein said preset allowable range of operation amount is determinedbased on said preset roll load.